In U.S. Pat. No. 5,487,012, a method is disclosed for manufacturing of a hearing aid housing comprising a hearing aid shell with an opening, and a face plate for covering the opening. The shell is individually matched to the shape of the auditory canal of a user. The method comprises the steps of a) direct or indirect acquisition of the shape of the auditory canal to obtain digital data representing the shape, b) conversion of the digital representation of the shape into a multi-dimensional computer model of the outer shape of the matching shell, and c) computer controlled production of the shell based on the data obtained from the three-dimensional computer model of the shell.
Problems relating to manufacture of the face plate are not recognized in U.S. Pat. No. 5,487,017.